# Differential pheromone profile as a contributor to premating isolation between two sympatric sibling fruit fly species

## TL;DR

This study finds that differences in pheromone profiles between two closely related fruit fly species may help prevent them from mating, even when they live in the same area.

## Contribution

The study identifies specific pheromone composition differences between two sympatric fruit fly species as a potential contributor to premating isolation.

## Key findings

- Differences in rectal gland pheromone composition were found between the two fruit fly species.
- Compositional variation included presence/absence and quantitative differences in compounds like alcohols, esters, and amides.
- Domestication of the species caused changes in pheromone profiles that could impact pest control methods like the Sterile Insect Technique.

## Abstract

Bactrocera tryoni (Froggatt) and Bactrocera neohumeralis (Hardy) are sibling fruit fly species that are sympatric over much of their ranges. Premating isolation of these close relatives is thought to be maintained in part by allochrony—mating activity in B. tryoni peaks at dusk, whereas in B. neohumeralis, it peaks earlier in the day. To ascertain whether differences in pheromone composition may also contribute to premating isolation between them, this study used solid-phase microextraction and gas chromatography-mass spectrometry to characterize the rectal gland volatiles of a recently collected and a more domesticated strain of each species. These glands are typical production sites and reservoirs of pheromones in bactrocerans. A total of 120 peaks were detected and 50 were identified. Differences were found in the composition of the rectal gland emissions between the sexes, species, and recently collected versus domesticated strains of each species. The compositional variation included several presence/absence and many quantitative differences. Species and strain differences in males included several relatively small alcohols, esters, and aliphatic amides. Species and strain differences in females also included some of the amides but additionally involved many fatty acid esters and 3 spiroacetals. While the strain differences indicate there is also heritable variation in rectal gland emissions within each species, the species differences imply that compositional differences in pheromones emitted from rectal glands could contribute to the premating isolation between B. tryoni and B. neohumeralis. The changes during domestication could also have significant implications for the efficacy of Sterile Insect Technique control programs.